1. Field of the Invention
This invention relates to a process for reducing surface irregularities of a coating upon a substrate in general and more particularly to a process for reducing surface irregularities of a photoresist or spin-on-glass coating upon a semiconductor wafer.
2. Description of the Prior Art
When a photoresist or spin-on-glass coating is deposited on a substrate pattern the coating is not totally planar because the coating somewhat follows the underlying contours of the pattern.
Prior art regarding reduction of surface irregularities on photoresist are disclosed in U.S. Pat. No. 5,395,803 (Adams). In this patent, coverings such as resist-type materials are dispersed onto a substrate in a spiral pattern to produce a more uniform coating than possible up to now. A method of planarizing spin-on-glass is disclosed in U.S. Pat. No. 5,454,871 (Liaw et al.). Here, a first coating of a silicate spin-on-glass is applied, filling the valleys of the irregular structure of the conductor layer. A second coating is then applied and both layers are cured. A uniform spin-on-glass dielectric layer is claimed.